Wireless power transfer

Wireless power transfer (WPT; also wireless energy transmission or WET) is the transmission of <a href="/facts/Electrical_energy/V0pJUrDY">electrical energy</a> without <a href="/facts/Wire/yyy05H1S">wires</a> as a physical link. In a wireless power transmission system, an <a href="/facts/Electric_power_source/w61ID9yQ">electrically powered</a> transmitter device generates a time-varying <a href="/facts/Electromagnetic_field/MacraS8y">electromagnetic field</a> that transmits power across space to a receiver device; the receiver device extracts power from the field and supplies it to an <a href="/facts/Electrical_load/IX0XBAqB">electrical load</a>. The technology of wireless power transmission can eliminate the use of the wires and batteries, thereby increasing the mobility, convenience, and safety of an electronic device for all users. Wireless power transfer is useful to power electrical devices where interconnecting wires are inconvenient, hazardous, or are not possible.
Wireless power techniques mainly fall into two categories: <a href="/facts/Near_and_far_field/wS2Dp5lv">Near and far field</a>. In near field or non-radiative techniques, power is transferred over short distances by <a href="/facts/Magnetic_field/Ta8Ev588">magnetic fields</a> using <a href="/facts/Inductive_coupling/6TfqcxdC">inductive coupling</a> between <a href="/facts/Electromagnetic_coil/fk2ElSDk">coils of wire</a>, or by <a href="/facts/Electric_field/tt4MooBs">electric fields</a> using <a href="/facts/Capacitive_coupling/7m9pjCPF">capacitive coupling</a> between metal <a href="/facts/Electrode/251PaKX8">electrodes</a>. Inductive coupling is the most widely used wireless technology; its applications include charging handheld devices like phones and <a href="/facts/Electric_toothbrush/wjkrxHNF">electric toothbrushes</a>, <a href="/facts/RFID/4CnmIV2b">RFID</a> tags, <a href="/facts/Induction_cooking/bkhxvd5K">induction cooking</a>, and wirelessly charging or continuous wireless power transfer in implantable medical devices like <a href="/facts/Artificial_cardiac_pacemaker/b90Qt8ND">artificial cardiac pacemakers</a>, or <a href="/facts/Electric_vehicle/jhCbx5ur">electric vehicles</a>. In far-field or radiative techniques, also called power beaming, power is transferred by beams of <a href="/facts/Electromagnetic_radiation/Ynx7ujCW">electromagnetic radiation</a>, like <a href="/facts/Microwave/HmVSN31Y">microwaves</a> or <a href="/facts/Laser/jk6PTvvT">laser</a> beams. These techniques can transport energy longer distances but must be aimed at the receiver. Proposed applications for this type include <a href="/facts/Solar_power_satellite/sQsRh0VI">solar power satellites</a> and wireless powered <a href="/facts/Drone_aircraft/qt87T19t">drone aircraft</a>.
An important issue associated with all wireless power systems is limiting the exposure of people and other living beings to potentially injurious electromagnetic fields.

Wireless power transfer open-in-new

Wireless power transfer